Ligation is a medical procedure in which an elastic ligating band, for example, is placed about tissue to prevent fluid flow therethrough. Where a ligating band is placed about, for example, a ballooning varix, polyp, hemorrhoid, or pre-cancerous lesion, a contracted ligating band induces fusion and healing in the base tissue and subjects the ligated tissue to necrosis. The necrotic tissue eventually separates from the surrounding tissue and passes into the human system. Alternatively, ligation may also be used for purposes of sterilization, wherein a ligating band may be placed over a folded loop portion of a Fallopian tube or a vas deferens to prevent the passage of internal reproductive fluids.
Means for delivering ligating bands, or ligating band dispensers, take various forms. One such form is a dedicated ligating band dispenser instrument which has a dispensing portion at a distal end, an actuating mechanism at a proximal end, and a typically rigid shaft therebetween. These instruments are useful for ligating tissue in which the user has access to the tissue to be ligated, e.g., tissue exposed through an invasive surgical procedure.
In contrast, ligating band dispensers may be positioned on the distal tip of an endoscope or a laparoscope. An endoscope is a conventional medical device used for viewing, exploring, and delivering therapies to internal regions of a patient. A laparoscope is a specialized endoscope for viewing a patient's peritoneal cavity. Unlike dedicated ligating band dispensing instruments, an endoscope allows minimally invasive intrusion into a patient.
FIGS. 1 and 2 illustrate a conventional endoscope. Endoscope 10 has a control portion 12 and a insertion portion 14 terminating at insertion tip 16. Insertion portion 14 is of such a length to permit access to internal regions of a patient.
FIG. 2 illustrates the face of insertion tip 16. A number of channels extend from the control portion 12 to the insertion tip 16, where the channels terminate in functional outlets 18-26. For the purposes of this example, outlet 18 is a light source; outlet 20 is a wide-field image sensing device, which transmits a video or fiber optic signal to a coupled monitor or eyepiece (not shown) at control portion 12; outlet 22 delivers a stream of water or air for clearing the image receiving device or flushing an internal bodily region; and outlet 24 is an outlet to a working (or biopsy) channel. Inlet 28 of the working channel can be coupled to a suction device or a lavage fluid source (not shown) or can receive various medical instrumentation (not shown) for passage through the working channel and outlet 24. Optional outlet 26, for larger diameter endoscopes, is an outlet for a second working channel. A second working channel allows additional operations in a manner consistent with the working channel described above.
Endoscope ligating band dispensers are fixedly mounted about and protrude from insertion tip 16 of a hosting endoscope, wherein such dispensers carry one or more expanded ligating bands about their outer diameter. Projecting from insertion tip 16, conventional dispensers inherently narrow the field of view of the image sensing device of outlet 20. In an effort to improve such impairment, some conventional devices are fabricated from a transparent material. While such material may facilitate the outward passage of light from outlet 18, such material does not practically improve the field of view for the wide-field image sensing device. Specifically, the use of transparent material commonly induces distortion about the periphery of a displayed image. Distortion is a product of both the curvature of the dispenser and the accumulation of bodily fluids about the outer surface of the dispenser. Ligating bands stored on the outer diameter of these dispensers further obstruct the field of view through the dispenser material.
Conventional endoscope ligating band dispensers commonly employ dispensing mechanisms which unnecessarily complicate a ligating procedure. Two examples of conventional mechanisms include a dispenser having a plurality of draw strings 1002 which are individually coupled to each of the stored ligating bands 1000 (FIG. 3) and a dispenser having a mechanically actuated housing which engages and requires movement of all stored ligating bands 1000 for each dispensing operation (FIG. 4).
In reference to FIG. 3, draw strings 1002 extend from each ligating band 1000 and around the distal end of the dispenser before extending proximally through the work channel of a receiving endoscope 10. Application of a proximally-directed force to a single draw string 1002 effects distal movement and dispensing of a coupled ligating band 1000. Understandably, during a procedure, a user must be keenly aware of which draw sting 1002 is being controlled to prevent the inadvertent dispensing of ligating bands 1000.
Referring to FIG. 4, another conventional dispenser example includes a mechanically actuated housing having a movable inner element 1008 and a fixed outer element 1010. Outer element 1010 carries a plurality of expanded ligating bands 1000, excepting the distal-most ligating band 1000a, which is carried by inner element 1008. For dispensing ligating band 1000a, element 1008 is drawn proximally, causing the distal-most ligating band 1000a to be released when inner element 1008 is pulled within outer element 1010. During such movement, the remaining ligating bands 1000 are displaced by shoulders 1012 so that when inner element 1008 returns distally, ligating bands 1000 are distally advanced. These conventional mechanisms require additional moving structure (for example, a spring 1014 to bias inner sleeve 1008 in a distal direction) which can increase the complexity, cost, and size of such devices. Additionally, attempting to maintain the dispenser at a reasonable length, the inclusion of elements such as shoulders 1012 may limit the number of ligating bands which may be stored.
Of further consideration, the dispenser of FIG. 4 can require an applied dispensing force having a magnitude sufficient to not only dispense a single ligating band but also distally displace the remaining stored ligating bands in preparation for a next ligation. As the number of stored ligating bands increase, the force necessary to move the ligating bands as a group also increases. Consequently, a user may experience some level of awkwardness during a procedure due to the force which may be necessary to dispense one or more ligating bands.
Conventional dispensers increase the length of insertion tip 16. A ligating band dispenser-equipped endoscope is commonly used within a hollow body cavity, for example, an esophagus. Insertion tip 16 must assume almost a 90.degree. bend with respect to the longitudinal axis of the insertion portion 14 to obtain a clear view normal to the inner surface of an esophagus. The additional length of the ligating band dispenser from insertion tip 16 can significantly restrict the motion and flexibility of insertion tip 16 within a hollow body cavity. Accordingly, the added length, coupled with the severely restricted peripheral view, makes the presence of conventional ligating band dispensers an operational liability during the exploration and placement phases of ligation procedures.